The International Cricket Council's controversial decision review system was in the spotlight again on the second day of the third Ashes Test at the WACA Ground on Saturday.

England were left disappointed when emerging batsmen Joe Root was given out caught behind by umpire Marais Erasmus at a crucial stage of the match from the bowling of Shane Watson in their first innings.

Root, who had made just four, was adamant he had not made contact with the ball and immediately challenged the decision.

The decision was then referred to New Zealand third umpire Tony Hill, who was himself at the centre of a massive controversy in the previous Ashes series in England, when he gave out Usman Khawaja from the bowling of Graeme Swann in the third Test.

Khawaja challenged the decision, but it was stunningly upheld by third umpire Kumar Dharmasena in a decision that caused a massive furore over DRS at the time.

The replays appeared to show that Khawaja hit his pad with the bat, rather than the ball, and it was one of several contentious DRS decisions during that series.

In Saturday's incident Hill watched numerous replays of the Root footage, but deemed it was largely inconclusive.

Hot spot showed no contact, while the audio evidence showed a faint noise as the ball passed the bat, although that could have been Root hitting his pad, as appeared to be evidenced by hot spot.

Hill decided there was not enough evidence to overturn the original decision and sent it back to Erasmus, so Root was on his way, shaking his head repeatedly as he departed.

Opener Michael Carberry was reluctant to discuss the decision, but said the English were certain that Root hadn't hit the ball.

"It was a disappointing dismissal for us and a key dismissal for us," he said.

"He felt he didn't hit the ball so he reviewed it.

"We are of the opinion he didn't hit, but the decision of the third umpire, we don't control it and it is one of those things we have to swallow.

"Obviously, we are bitterly disappointed."

Erasmus also had one of his decisions overturned earlier in the day, when he gave centurion Steve Smith not out caught behind, only for Hill to overturn the decision on audio evidence.

Eccentric New Zealand umpire Billy Bowden also had mixed fortunes on the opening day, when he twice miscounted balls in an over.